Adsorption and reactivity of NO and N2O on Cu{110}: Combined RAIRS and molecular beam studies

The interaction of NO with Cu{110} is complex and is strongly dependent on both coverage and temperature, When Cu{110} is exposed to NO in the temperature range 40-85 K, initial adsorption leads to the presence of molecular NO on the surface, With further exposure this is replaced by the dimeric (NO)(2) species and N2O. Below 60 K, subsequent adsorption leads to the formation of multilayers of (NO)(2). A detailed molecular beam study shows that adsorption is accompanied by the appearance of a range of gaseous reaction products. At 85 K, beaming of NO at a Cu{110} surface results in a large uptake of NO, which leads to gaseous N-2 and N2O production followed by a sudden saturation of the surface. The observed gaseous products are. derived from adsorbed N2O formed on the surface upon exposure to NO, which dissociates to give the observed gaseous N-2 and O-ad. This was confirmed in independent experiments with N2O beams, demonstrating gaseous N-2 production at 85 K. Saturation of the surface with O-ad results in a sudden fall in NO uptake. At higher temperatures N-ad, which associatively desorbs as N-2 at similar to 800 K, is also produced on the surface by dissociation of incident NO. The NO dissociative sticking probability passes through a maximum. at 200 K, with an anomalously sharp fall between 220 and 300 K